Lightweight recoilless gun



May 5, 1959 L. SHAPIRO ETAL LIGHTWEIGHT RECOILLESS GUN 3 Sheets-Sheet 1 Filed Deb. 12, 1958 4 v N J 2 uv mR mm m m 3 2 g 2 0 I I I 2 @b ml 9 w ATTORNEYS May 5, 1959 L. SHAPIRO ETAL 4,

' LIGHTWEIGHT RECOILLEISS GUN 3 Sheets-Sheet 2 Filed Dec. 12, 1956 FIG. 9

JNVENTORS. LEO SHAPIRO. ANDREW ST. JOHN.

FIG. 5.

ATTORNEYS;

L. SHAPIRO ETAL LIGHTWEIGHT RECOILLESS GUN May 5 1959 3 Sheets-Sheet 3 Filed Dec. 12, 1956 FIG. IO.

FIG. ll.

FIG. I2.

@ INVENTORS. LEO SHAPIRO. ANDREW D. 51'. JOHN.

36 wfo lujmm 73 4mm,

ATTORNEYS United States Patent Ofiice 2,884,837 Patented May 5, 1959 LIGHTWEIGHT RECOILLESS GUN Leo Shapiro and Andrew D. St. John, Prairie Village, Kans., assignors to the United States of America as represented by the Secretary of the Army Application December 12, 1956, Serial No. 627,969

2 Claims. (Cl. 891.7)

The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment of any royalty thereon.

This invention relates to a recoilless gun and has for an object to reduce the weight thereof. Another object is to reduce the quantity of unburned ammunition that may be lost out the rear of the venturi passageways used to overcome recoil in such a gun.

The customary recoilless rifle has used ordinary grains of propelling charge which are burned in a cartridge case provided with many perforations in the sides of the case and through which gases may issue radially into an ambient chamber and then those products of combustion are directed rearwardly through the usual venturi passageways in overcoming thrust of recoil. The wall of this gas chamber around the cartridge case and extending longitudinally for at least about the length of the portion of the cartridge case occupied by the propelling charge, has been found to contribute a substantial amount to the weight of the gun. If the bore of the gun were extended rearwardly from the projectile receiving cham her and the customary grains of propelling charge material were used, the loss through the unburned particles blown rearwardly would be enormous.

According to this invention, the weight of a recoilless gun has been reduced by as much as about 25% or more through elimination of the large rear ambient gas chamber and large breech block, thus enabling less metal to be required for a gun of smaller diameter at its rear end portion. The danger of high loss of unburned particles of propelling charge has been reduced by the use of connected layers of sheet material whereby the connection between the layers assists in holding the material until more fully burned, as stacked disks of sheet material whereby the disks are held on a central rod until more nearly fully burned.

Fig. 1 shows a rear view of a gun embodying this invention.

Fig. 2 is a section of the line 2-2 of Fig. l with a sheet propellant charge in place and partially broken away.

Fig. 3 is a section on the line 3-3 of Fig. 1 showing the contour ofthe bar shaped breech block.

Fig. 4 is arear view of the gun of Figs. 1 to 3 inclusive but with the breech bar in a generally vertical and unlocked position.

Fig. 5 is a horizontal sectional view of the gun looking down upon the top edge of the unstanding breech bar of Fig. 4.

Fig. 6 shows a sectional view of one embodiment of sheet propellant for use in the present gun taken on the line 6-6 of Fig. 7.

Fig. 7 is a section on the line 7--7 of Fig. 6.

Fig. 8 shows another type of sheet ammunition within a gun.

Fig. 9 is a partial section on the line 9-9 of Fig. 8 showing the ammunition.

Fig. 10 is a rear end view of a gun containing another embodiment of this invention.

Fig. 11 is a section on the line 11-11 of Fig. 10.

Fig. 12 shows a view corresponding to Fig. 11 but With the breech bar of Fig. 11 not in section and not fully closed.

A rear end portion of a recoilless gun 10 is provided with the usual outwardly and rearwardly flaring or tapered portion 11 leading from the chamber 12 which is of very nearly bore-size and into which ammunition is placed. A bar shaped breech block 13 closes a part of the rear end of the gun when loaded. This bar shaped breech block is provided with a projection or handle 14 pivoted on the pin 15 to a supporting and binge bar 16 which in turn is hinged to the gun through the hinge pin 17. This bar shaped breech block is of general airfoil contour indicated in Fig. 3. An abutment 18 shown in Figs. 1 and 2 provides a stop against which the handle for the breech block rests when in fully closed position. The metal pad 19, shown in Fig. 2, is pressed by the spring 20 against a depression 19a (Fig. 3) or a flat spot on the pivot pin 15 to assist in holding the breech block in its open position (Fig. 4). One or more lugs 21 on this breech block of the general shape indicated in Fig. 2, cooperate with grooves 22 between the lugs 21 shown in the gun and constitute the functional equivalent of an interrupted thread as is common in breech blocks. A great deal of wear in a recoilless gun occurs and is taken up by the wear-resisting inserts 23 which are preferably four in number, two being angularly long and nearly semicircular in shape, two others are short. These inserts are preferably held in place by one or more threaded bolts 24 as shown in Fig. 2. The usual rifling 25 is provided for the projectile receiving portion of the gun and extends forwardly thereof. This rifling may also extend rearwardly into some portion of the propelling charge receiving chamber, if desired, inasmuch as it is more economical to manufacture a fully rifled tube than one which is only partially rified. The gun of this invention need not be rified at all.

As shown in Fig. 3 the opposite faces 26 and 27 of the bar type breech block are fiat and constitute portions of the venturi walls. The opposite faces of the venturis are nearly semi-circular in shape and constituted by the outwardly flared portions 11. Thus, in this invention there are two venturi passageways, one on each side of the bar shaped breech block. The forward side of this breech block is rounded at 28, as shown in Fig. 3. Each venturi construction occurs between the wear-resistant inserts 23 and a point 29 on the breech block where it is of maximum thickness.

The breech bar 13 and its operating handle 14 are shown in Fig. 4 in an upright and unlocked or open position ready to be swung outward for insertion of the projectile and propelling charge. The projectile and said charge may be loaded separately or as a unit.

Regardless of whether the ammunition be separate loading, the preferred form is not in the usual cartridge case or bags but is in sheet form of the type disclosed in the prior invention of Kroeger and Schecter, Serial No. 619,644 filed October 31, 1956, for Sheet Ammunition and shown herein in Figs. 6 to 9 inclusive. One reason for the preference for sheet ammunition for use in the gun of the present invention is the fact that the sheet portions are connected whereby during combustion there is less likelihood of unburned particles being blown outwardly than would be the case where the grains discrete.

In Fig. 6 is shown one embodiment of a sheet propelling charge, the same being in roll or scroll form. The sheet ammunition 30 is provided with a number of dimples (,3 or stam ed out protuberances 31 for spacing layers of the sheet. Suchspacing enables products. of combustion to move rearwardly during burning and out the venturi passageways without as great danger of unburned particles of sheet material being blown outward as would be the case were the particles ofpropelling charge not connected initially. The sheet ammunition 30 may be provided with a central supporting tube having many perforations. and filled with black powder, asis the form of sheet ammunition shown in Figs. 8 and 9. n ignition by a primer, not shown, flames from the powder issue through the holes in the supporting tube and ignite the roll at numerous places. Fig. 7 is: a section on the. line 7-7 of Fig. 6 but said figures are; not in alignment.

Fig. 8 shows discs of sheet ammunition. also disclosed.

and; claimed in the. aforementionedapplication of. Schccter an Kr eg r- Herehe discs. 32, are preferably spaced pa by i ple or; button-like:protuberances 33 These nection and support for the discs during combustion to minimize the likelihood of disc. portions flying out prematurely. The support 35 contains black powder and on ignition flames therefrom isue through the numerous perforations to ignite the discs at numerous places longitudinally of such support. Either the roll or disc type sheet ammunitionmay be used with fixed or separate loading ammunition and also with a fin or spin stabilized projectile. Thus the supporting tubes for the ammunition of Figs. 6 to 9, inclusive may be part of the projectile or for some types of separate loading this, tube may be part of the propelling charge and not attached to the projectile. Where this tube is consumable it is usually not an important part of the propelling charge. Below the discs 32 in Fig. 8 is shown the endofa projectile 35a. The use of the bar shaped breech blockwith a propelling charge receiving chamber of bore size enablesthe gun to be of light weight and the use of the sheetammunition permits a reduction in loss of propelling charge particles and therefore contributes to the weight of this gun being less than has heretofore been the practice.

In Figs. to 12 is shown another. embodimentof this invention in which the usual. bar shapedflbreech. blockv 3.6 is provided with a projection or-handle37 andis pivoted directly to a rear end portionofthe gun. Lateral. holes 38 and 39 in the sidewalls in therear end of thegun cooperate with holes 40 in the bar-breechblock 36'to enable retaining pins 41 and 42 to be inserted for holding the breech block in closed position. This embodiment possesses the usual venturipassageway disclosed in Figs. 1 and 2.

Among the advantages of this invention may be mentioned fiiSlI' the substantial reduction in weight of a recoilless rifle by as much as about 25% or. more. The breech block beingof abar type is a factor contributing to this reduction in weight. The breech block forms'two venturi passageways,.and provides thrust walls for. the expanding gases. The bar shaped breech blockconstitutes a large portion of the venturi surfaces as'nearly-the entire surface of the bar shaped breech block-is a portion of. some venturi passageway. The'use ofsheet'ammunition with a gun of this type contributes'to a reduction in loss of propelling charge and reduces the amount ofsuch charge which would otherwise be blown out rearwardly and rendered useless. The sheet ammunition illustrated is shown as having internal portions thereof connected during combustion and this fact is another factor contributing to reduction in such losses. The sheet propellant had a nominal composition as follows: nitrocellulose 12.2 to 13.35% N 56.74%, nitroglycerine 35%, ethyl centralitc 7.95%, graphite 3%, moisture and volatiles .5 or less. The sheet had a thickness of about .045 inch, the protuberances about .10 inch in diameter by about .017 inch in height and arranged with about .34 inch between centers. The thickness of the sheets varied from about .025 to .075 inch.

We claim:

1. A recoilless gun having a'substantially bore size propellant chamber, a transverse bar shaped breech block having the opposite sides thereof tapered to constitute portions of venturi passageways when said breech block is locked in place, said bar shaped breech block being generally streamlined in transverse cross-section, asupporting'ba-r. for the bar shaped breech block, said supporting bar being hinged to. said gun, alined with said bar shaped breech block when closed and not substantially thicker radially than a longitudinally outer face thereof, a pivot on which said bar shaped breech blockv is carried by said supporting bar, locking means between the breech block and an inner surface of the gun. for holding saidv breech block, in its. closed position, and a projection on said breechblock by which it may be rotated on its pivot in moving it toandfrom open and closed position, the rear'inner end of said gun. on. opposite sides of said breech block whenclosed being tapered to form venturi passageways with thetaperedsides of said breech block, whereby the bore size chamber, together with the bar type breech block are elfective in eliminating the necessity for gas passages and venturi openings largely radially outside of a bore; diameter-and effective in substantially reducing the weight of. said gun.

2. A recoillessgun having a substantially bore size propellant chamber, a transverse bar shaped breech block having the opposite sides thereof tapered to constitute portions of venturi passageways when said breech block is locked in place, said. breech block being generally streamlined1 in. transverse cross-section, provided with a hinged support on which. it may be swung out of the way. for. loading, said hinged support being attached directly to said. gun, locking pins. transversely movable through .a wall. of the gun,, into and out of said breech block for locking the same. in closedposition, and a projection on. said breechblock by means ofwhich itmay be swung to.

auopenandclosed position, on saidhinged support, the

rear inner. end. of said. gunonopposite. sides. of .said breech block whenclosedbeing tapered to form venturipassageways. with thetapered sides of said.breechiblock,.whereby. the bore sizechamber, together with thebar. type breech block are eifectivein eliminating the necessity for. gas

passages and venturi openings largely radially outside of.

abore. diameter and effective in substantially reducing the weight of said gun.

References Cited in the file of this patent UNITED STATES PATENTS 

